The present invention generally relates to methods and systems for fabricating elastomer-based electronic devices. The invention particularly relates to methods and systems for fabricating elastomer-based electronic devices, as a nonlimiting example, an elastomer-based strain sensor of a wearable sensory garment.
Liquid-conductor embedded elastic sensors generally comprise liquid-conductor traces embedded within an elastomer material. As nonlimiting examples, such sensors have found use as elastic strain sensors for artificial skins and wearable exosuits, wearable tactile keypads, and non-differential elastomer curvature sensors. Various processes can be used to fabricate liquid-conductor embedded elastomer sensors, for example, by injecting a liquid conductor into a cavity between individually-cast elastomer components that have been bonded together, or by encapsulating a liquid conductor that has been direct-written on an elastomer substrate, or embedded 3D printing by extruding conductive fluid inside of uncured elastomer material. The sensors may then be integrated onto a substrate, for example, the fabric of an exosuit, artificial skin, or other wearable sensory garment, using straps, hook-and-loop fasteners, and adhesives, as nonlimiting examples.
Other types of elastic sensors utilize electrically-conductive elastomer films as one or more of their electrical components. One of the challenges of using conductive elastomer films in highly deformable sensors is the tendency for their material properties, including electrical conductivity (resistance) and Young's modulus, to change over time. Consequently, conductive elastomer films tend to be more suitable for use in roles other than the sensing element, for example, when used as the electrodes of a capacitive sensor. Many examples of capacitive sensors appear in the soft electronics literature, including those for sensing strain, pressure, and proximity. Such sensors have been reported as fabricated from a variety of materials, including metal electrodes, carbon nanotubes, liquid metals, printed conductive inks, conductive elastomers, graphene-filled sponges, conductive fibers, silver nanowires, and salt solutions. Although these examples utilize different fabrication methods and materials, the diversity of approaches illustrates the underlying utility of capacitive sensing in many applications.
Complications encountered when incorporating elastic sensors into wearable sensory garments include the flexibility of the sensor's electrical components, the preparation of the garment fabric, and adhesion of the sensor to the garment fabric. The manufacture process is often separated into multiple steps, such as those noted above, creating need for oversight and additional costs. As such, there is an ongoing need for less complicated methods suitable for manufacturing elastic sensors, including but not limited to elastomer-based sensors incorporated into wearable sensory garments.